I often see ads that advertise amplifier output power and my first question to the advertiser is, "At that maximum power level, is that amplifier operating in the linear portion of the power output curve or is it driven into saturation?" If your quest is for an amplifier to be used for Radio-Telephony, in this case SSB phone, then you MUST be concerned with the linearity of your power amplifier unless you want a signal that is generating strong odd order distortion products across the adjacent spectrum. The way you can easily measure linearity is to check input power against output power. As input power is increased, the output power level should increase proportional to the gain of the amplifier stage. When you start to see a reduction in output power vs. input power, you have driven the amplifier into compression and it is no longer linear. A good example of this is the Mirage 1016 amplifier. If you apply drive to it, it will product good results up to about 100 watts output but if driven to 160 watts, you should only be using either CW, FM, or Digital modes because it is fully driven into compression and will produce wide-band splatter. So, keep this in mind when you are purchasing an amplifier, particularly on old design that was built when the maximum power INPUT POWER to the output stage was 1KW and in the case of grounded grid amplifiers, that one KW included the drive power to the cathode or cathodes.